1. Field of the Invention
This invention relates to the general field of securing a payload in and deploying a payload from the cargo bay of a space vehicle. The payload must be secured to withstand stresses generated by launch, abort, deployment, recovery and landing. In addition, the payload must be easily deployed from the cargo bay once the vehicle is in space. The invention particularly relates to a reusable space vehicle like the orbiter in the NASA Space Transportation System (STS). In the preferred embodiment, the subject invention can be used to secure in and deploy from the orbiter a payload consisting of an upper stage and a mated spacecraft, such as a communications satellite.
2. Brief Description of the Prior Art
The prior art discloses several different designs for cradle structures to be used to support payloads in space. U.S. Pat. No. 4,324,374 issued to Wittman discloses a single, U-shaped cradle with three points of attachment between the payload and the cradle. The payload is positioned in the cradle so that the center of mass of the payload lies in the same plane as the three points of attachment. To deploy the payload, locks located at two of the three points of attachment are released. The connection at the third and final point of attachment is then released by an explosive separation, thereby allowing a single spring to impart translation and rotation to the payload.
While the use of a single cradle does provide support in the lateral and longitudinal (X and Y) directions as well as in the gravity (or Z) direction, this system has a disadvantage in that a single cradle is best suited for payloads which are small in size and light in weight. A larger payload would be more efficiently supported by use of both forward and aft connections between the payload and the cradle. Moreover, the support provided by the single cradle is limited to attachments at three points. As a result, the load at each point of attachment is greater than if additional attachment points were used.
A single, continuous retention cradle to support a payload during launch or retrieval missions is disclosed in an article by Ceppollina and Mansfield (Astronautics and Aeronautics, February 1975, pp. 48-56). That cradle consists of three sections which are hinged together. Each of the three sections, two upper hinged sections and a fixed bottom section, has a V-groove connection which mates with a corresponding ring around the circumference of the payload. A separate positioning structure, which also is located in the cargo bay, is used to move the payload from the retention cradle to a deployment position. The payload is supported by a continuous support system.
However, like the device disclosed in Wittman, the retention cradle disclosed by Ceppollina has certain disadvantages. First, the retention cradle has only a single ring and thus may not be suited for supporting larger payloads. Second, the use of a continuous V-groove connection requires that the payload be equipped with a corresponding ring, which adds weight to the payload to be launched and deployed in space. Finally, the deployment mechanism for the Ceppollina retention cradle is separate from and not integrated into the cradle, thereby adding weight and consuming additional space in the cargo bay of an orbiter.
U.S. Pat. No. 4,044,974 issued to Lingley discloses a single-hinged cradle structure with forward and aft connection rings to support a payload in the cargo bay of a space vehicle. Both the forward and aft connection rings, referred to as continuous integrated normal clamping hoop (CINCH) rings, are attached to a single box frame structure. Those rings completely surround a portion of the payload and mate with corresponding connection rings attached to the payload. The payload is deployed after the upper half of the hinged cradle and the attached payload are rotated into the open position.
While the Lingley device has the advantage that the cradle provides continuous forward and aft support for the payload, the device has at least four significant limitations. First, the continuous rings that are attached to the payload and the box frame structure may deform when subjected to the extremes of heat and cold in space prior to deployment. Thus, if a deployment has to be aborted, any differential deformation between the payload and the cradle may prevent the cradle from closing around the payload.
Second, the ring structure described by Lingley is suitable only for a payload which has a regular annular surface which conforms to the annular shape of the cradle. Restricting the shape of the payload to an annular shape limits design flexibility because specific payloads having an irregular shape may be desirable in some instances. The alternative of adding an annular ring around a non-annular payload adds undesirable weight and bulk to the payload.
Third, the Lingley cradle comprises a single box frame structure which supports both the forward and aft connection rings. The box frame structure creates extra weight and takes up space in the cargo bay of he orbiter.
Fourth, forward and aft interface rings must be attached to the spacecraft, thereby increasing the weight and volume of the spacecraft.
Another cradle design, which was developed by Boeing Aircraft Corp. for the Inertial Upper Stage (IUS) system, comprises a forward cradle and an aft cradle. The payload is attached to the forward U-shaped cradle by means of payload retention latch assemblies (PRLAs). The payload is attached to the aft cradle by means of a continuous connection between the aft end of the payload and the aft cradle. The aft cradle tilts and permits the payload to be deployed.
There is no direct structural connection between the forward and aft cradles. Certain longitudinal loads are transferred from the forward and aft cradles through the frame of the payload. Other longitudinal and lateral loads are transferred from the forward cradle to the frame of the orbiter by means of load levelers and a low response damper.
The IUS cradle has certain limitations. First, the forward cradle relies on point attachments to the payload provided by the PRLAs. Use of these point attachments may result in significant differential loading on the forward cradle during launch and requires that the forward cradle be reinforced to withstand the relatively large moments produced by movements of the payload. Second, the aft cradle consists of a frame structure which takes up additional space in the cargo bay of an orbiter. Third, the aft cradle is attached to an orbiter by an assembly which includes a slip ring, a low response spreader beam and a spring and damper assembly. This assembly adds weight and complexity to the aft cradle.
Accordingly, it is an object of the present invention to provide a lightweight support system for securing a heavy payload in the cargo bay of a reusable space vehicle during all phases of operation.
Another object of this invention is to provide a reliable support system which provides for the easy deployment of the payload from the cargo bay.
A further object of this invention is to provide a flexible support system which is capable of securing a payload which has an irregular shape.
Yet another object of this invention is to provide a support system which has the capability to easily deploy a payload in space and to secure a payload which has been prepared for deployment in space but has had the deployment aborted.